In March 2010, the Health Care and Education Reconciliation Act was passed in the United States, and personalized health care was included in this Act. The testing of biomarkers is one of the key technologies in personalized healthcare. Currently, concentrations of biomarkers range from 101 to 10−12 mg/mL (ppt), including as high as 13 orders of magnitude. For thousands of testing procedures, each of them should be completed with 50-500 nanoliters (nL) of blood plasma; in such volumes, the numbers of molecules which have very low concentrations are relatively rare. However, for the testing of low-concentration samples, the volumes of the specimens is too little to become invalid samples. Therefore, a microchannel which is able to both contain sufficient samples and rapidly concentrate biomarkers is important for testing.
Dielectrophoresis is a kind of method to effectively concentrate protein.
However, dielectrophoresis with metal electrode has problems such as electrode hydrolysis, low concentration efficiency, and generation of joule heat. In recent years, electrode-less dielectrophoresis has been developed to resolve the problems in dielectrophoresis with metal electrode. According to the dielectrophoresis equation (FDEP=2πa3εmRe(K*(ω))∇E2), in order to generate enough dielectrophoretic force, a great enough electric field gradient is required. Electrode-less dielectrophoresis mainly uses a structural design to generate a condensed electric field. There are different designs such as a rectangle, a column, and a triangle. The use of a design of a triangular condensed structure which is able to completely concentration the sample at a structural limiting space is the most efficient condensing method. However, since a nanostructure is manufactured by electron beam lithography, when used in conjunction with a channel about 100 nm deep, a reaction volume is only at the picoliter (pL) level. The molecular sizes of some biomarkers are about several tens of nanometers. However, in such low reaction volumes, for the testing of very low concentrations, the number of molecules included in such volumes are relatively reduced, even to zero.